Displacement >5 mm of a larger fragment is managed by fragment osteotomy, soft tissue release, capsulotomy through the rotator cuff interval, or a subscapularis split and fixation with plate, cannulated screws, and bone suture [19, 20].

If the fragment is still retracted and not sufficiently mobile after capsular and subacromial release, the rotator cuff interval must be opened completely.

Fragment reduction and fixation must be preceded by accurate decortication of bone surfaces, since bleeding is indispensable for the healing process; in some cases, autologous or synthetic bone grafts may be used [21].

If the fragment cannot be mobilized completely, it should be fixed in a more appropriate position with the arm in internal or external rotation and restored to its anatomic location as closely as possible [22].

In malunion secondary to three- or four-part fractures with congruent articular surfaces and no avascular necrosis or pain, surgery should be considered in relation to the residual ROM and to functional impairment.

Anterior elevation >120° and external rotation >30° rule out osteotomy and should entail arthroscopic capsulotomy and subacromial debridement, whereas elevation <120° and external rotation <30° require corrective osteotomy and fragment fixation [23].

Prosthetic replacement is indicated when malunion has severely damaged the head joint surface resulting in incongruent articular surfaces or head necrosis [24] (Figs. 13.3 and 13.4).

This situation is found more commonly in three- and four-part fractures, humeral head-splitting fractures, posttraumatic arthrosis, and head bone defects due to impact trauma involving >40 % of the articular surface [25, 26].

Implant selection is a function of the anatomo-pathological findings. Young patients with head necrosis are usually treated with hemiarthroplasty or resurfacing, whereas an anatomic prosthesis is preferred in patients with concentric posttraumatic arthrosis and a damaged glenoid articular surface [27].

In patients older than 65 years with a poor or absent rotator cuff, reverse shoulder arthroplasty is preferred [28].

Prosthesis implantation in a shoulder with a malunited fracture is a complex procedure, due to the abnormal position of the tuberosities and humeral head and to the retraction of capsular, ligamentous, and musculotendinous structures.

All precautions should be enacted to achieve optimum capsular and subacromial release.

The risk of postoperative complications is high due to the complex nature of malunited proximal humeral fractures .

Besides the general risks related to surgery, procedure-specific complications may also arise, such as resorption of the tuberosities, fragment pseudarthrosis , and loosening of fixation [29].

Most patients are elderly with poor bone stock due to osteoporosis, a condition that greatly increases failure rates [30].

Humeral head vascularization is often damaged by the initial trauma, increasing the risk of necrosis after osteotomy [31].

Neurological lesions and infections are further potential complications whose incidence is related to the quality of surgery and antibiotic prophylaxis.